{ INFORMATICS.MCCME.RU
  Problem statement: http://informatics.mccme.ru/moodle/mod/statements/view3.php?chapterid=109
  Verdict: Accepted
}
uses SysUtils, Math;
 
var
	ls,i:longint;
	s:string;
 
begin
reset(input,'input.txt');
rewrite(output,'output.txt');
readln(s);
ls:=length(s);
for i:=1 to ls do
	if pos(s[i],s)<i then begin
		write(s[i]);
		break;
	end;
end.